复杂载荷作用下立管触地段损伤管道的动力响应

Dynamic Response of Damaged Riser in Touchdown Zone Under Complicated Loadings

触地段(Touchdown zone, TDZ)是在役钢悬链线立管(Steel catenary riser, SCR)的关键部位,在复杂载荷作用下,极易形成损伤缺陷,其载荷寿命的评估是深海结构工程中的一个关键问题。本文以大型有限元软件ABAQUS为平台,运用损伤管道实体单元与土弹簧阻尼单元相互作用的模型模拟触地段损伤海底管道在复杂载荷作用下的动力响应,数值计算考虑了管-土相互作用过程中的材料非线性、几何非线性以及接触非线性。讨论了单一环向体积损伤位于触地段管道的不同位置时,触地段损伤管道在不同载荷作用下的动力特性及特征点的动力响应。结果表明,管道所受内外压力以及管道提升端的竖向位移载荷会影响结构的自振频率;体积损伤部位的动力响应较完好部位更剧烈;体积损伤的位置和动力载荷频率对管道动力放大系数的影响很大;当动力载荷的激励频率越接近结构基频时,损伤管道的动力响应及动力放大系数越大。

In deep sea engineering,steel catenary riser(SCR) is an important structure in connecting platform and subsea pipeline. It consists of catenary zone, touchdown zone(TDZ) and surface zone. The touchdown zone is one of the most important parts of the steel catenary riser under the complicated loadings in marine environment. As the floating platform is relatively flexible compared with the fixed offshore platform and will generate some vibration and drift in the complicated marine environment. The movement of platform would induce the vibration and damage in TDZ. It is the key issue to evaluate the service life for the SCR with fault and damage in the deepwater. A computational model, which is with the feature of the solid-soil interaction under the complicated loadings, is proposed herein. The response of the TDZ with damages is calculated by using the model upon the software ABAQUS. The nonlinearity of material and geometry, as well as the contact situations, are accounted. The dynamic characteristic and dynamic response of the pipeline with the single circular volume defect on the different positions with different scales of working loadings and environmental loadings are also discussed.The results show that the stiffness and the frequency of the pipeline is changed with the internalpressure, external pressure and vertical displacement on the lifting end. Stress response in defect zone was more severe than the intact zone. Dynamic amplification factors are largely affected by the positions of the volume damage and the foundational frequency of the dynamic loadings. The research results is valued to estimate the life of the pipelines with damages under the action of the multiple loads.